This invention relates to a distributed, broadband cable sending and receiving system wherein a single transmission medium is used to carry voice and data information between a central office location and multiple subscriber locations.
It is well known in the art that cable television systes using coaxial cable, and telephone systems using twisted pair cable, as the transmission mediums, are capable of delivering voice and data services by means of analog or digital carrier systems, or by the use of modems. Existing digital systems are primarily used to carry a large number of multiplexed voice circuits from one point to another. The purpose of the present invention is to distribute both voice and data information.
Existing distributed digital systems using multiplexed digital baseband transmission have a cost disadvantage relative to the present invention because the higher bit rates necessary to service each subscriber location require more expensive circuit components and require more complex framing and demultiplexing tasks to be performed at each subscriber location.
Existing analog carrier systems have a greater susceptibility to noise and beat-frequency interference than digital systems and are not designed to provide both voice service and high speed data services without additional subcarriers or modems. Existing analog, distributed carrier systems also generally use a separate set of allocated frequencies for each subscriber, making it necessary to use greater bandwidth on the transmission medium relative to the present invention due to the necessity of having spectrum dedicated to subscribers when they are not sending or receiving information.
Existing data modems can be used to transmit and receive both voice and data services but are not currently cost-effective since their polling, addressing or contention formats are optimized for data transmission. And existing systems do not use a combination voice and data format to provide a uniform voice sampling rate with low bit overhead.